The present invention relates to a coil instrument which rotates a rotor magnet by energizing a coil, for example, a coil instrument incorporated in a combination meter for a vehicle.
As a coil instrument applicable to a meter for vehicle, for example, a cross-coil instrument has been generally well known. The cross-coil instrument is called xe2x80x9can air core type movementxe2x80x9d and is constituted such that a rotor magnet is accommodated in a space defined in a housing, a rotor shaft fixed to the rotor magnet is pivotally supported on the housing, one end of the rotor shaft is protruded to the outside of the housing, a pointer is mounted on a protruded end of the rotor shaft, and a pair of coils are wound around an outer periphery of the housing in such a manner that the coils cross at a right angle. The rotor magnet (pointer) is rotated due to a resultant magnetic field generated by energizing respective coils. By controlling energizing quantities (inputting signals) to respective coils in response to a measured quantity, the pointer can be angularly moved in response to the measured quantity.
By the way, in such a cross-coil instrument, it has been known that due to the winding diameter dimension difference and the magnetic hysteresis or the like of respective coils which are generated by winding a pair of coils in layers in a crossing manner, an error occurs on a rotating angle (an output angle) of the pointer in response to an input signal and this error appears as the indication error. To cope with this, as disclosed in Japanese Laid-open Patent Publication 27146/1994, it may be possible to propose an idea that a pointer shaft on which a pointer is fixedly mounted is provided independently from a rotor shaft on which a rotor magnet is fixedly mounted and both of these shafts are connected by way of gears so as to rotate the pointer shaft at a reduced speed compared with the rotor shaft whereby the occurrence of the indication error can be suppressed.
However, the cross-coil instrument disclosed in the above-mentioned publication has a drawback that in addition to the constitution that a pair of coils are wound around the housing in a laminated manner, gears are further stacked on the housing around which the coils are wound, the height dimension of the instrument becomes large so that the instrument has to become large-sized.
The present invention has been made in view of the above and it is a main object of the present invention to provide a coil instrument which can maintain a compact constitution even when a pointer-side rotary shaft is rotated at a reduced speed by way of gears.
The coil instrument according to the present invention comprises a rotor shaft having a rotor magnet and a first gear rotatable along with the rotor magnet, a pointer shaft having a second gear connected with the first gear, and a pair of coils arranged such that the coils opposedly face an outer peripheral surface of the rotor magnet where the second gear is not arranged and give a rotational force to the rotor magnet upon energization thereof. Due to such a constitution, even when the rotary shaft at the pointer side is subjected to the deceleration rotation by way of gears, the compact coil instrument can be provided.
Further, the coil instrument according to the present invention comprises a rotor shaft having a rotor magnet and a first gear rotatable along with the rotor magnet, a pointer shaft having a second gear connected with the first gear, a housing supporting the pointer shaft and the rotor shaft in parallel, and a pair of coils arranged such that the coils opposedly face an outer peripheral surface of the rotor magnet where the second gear is not arranged and give a rotational force to the rotor magnet upon energization thereof. Due to such a constitution, even when the rotary shaft at the pointer side is subjected to the deceleration rotation by way of gears, the compact coil instrument can be provided.
Further, the coil instrument according the present invention comprises a rotor shaft having a rotor magnet and a first gear rotatable along with the rotor magnet, a pointer shaft having a second gear connected with the first gear, and a pair of coils arranged such that the coils opposedly face an outer peripheral surface of the rotor magnet where the second gear is not arranged in a state that respective winding central axes of the coils cross each other with a given crossing angle at or in the vicinity of the rotary center of the rotor magnet and give a rotational force to the rotor magnet upon energization thereof. Due to such a constitution, even when the rotary shaft at the pointer side is subjected to the deceleration rotation by way of gears, the compact coil instrument can be provided.
Further, the coil instrument according to the present invention comprises a rotor shaft having a rotor magnet and a first gear rotatable along with the rotor magnet, a pointer shaft having a second gear connected with the first gear, a housing supporting the pointer shaft and the rotor shaft in parallel, and a pair of coils arranged such that the coils opposedly face an outer peripheral surface of the rotor magnet where the second gear is not arranged in a state that respective winding central axes of the coils cross each other with a given crossing angle at or in the vicinity of the rotary center of said rotor magnet and give a rotational force to the rotor magnet upon energization thereof. Due to such a constitution, even when the rotary shaft at the pointer side is subjected to the deceleration rotation by way of gears, the compact coil instrument can be provided.
Further, in the coil instrument according to the present invention, the crossing angle made by the winding center axes of respective coils is set to approximately 90 degrees. Due to such a constitution, the magnetic field vectors generated at respective coils cross at an approximately right angle and hence, magnetic forces of the coils can be made to effectively act on the rotor magnet.
Further, in the coil instrument according to the present invention, the crossing angle made by the winding center axes is set to less than 90 degrees. Due to such a constitution, the width dimension of the housing including the coils can be made small.
Further, in the coil instrument of the present invention, the rotary center of the rotor magnet is positioned closer to the coil side than the crossing point made by the winding central axes of the respective coils. Due to such a constitution, the width dimension of the housing including the coils can be made small.
Further, in the coil instrument of the present invention, the first gear is provided with first continuous teeth on an outer periphery thereof, the second gear includes a accommodating portion which accommodates the first gear on an outer periphery thereof, and second continuous teeth which are meshed with the first continuous teeth are formed on an inner periphery of the accommodating portion. Due to such a constitution, while realizing the deceleration rotation of the pointer shaft to the rotor shaft, the rotor shaft and the pointer shaft can be made to approach each other and hence, the width dimension of the coil instrument can be made small by an approaching quantity.
Further, in the coil instrument of the present invention, an outer diameter of the first gear is smaller than an outer diameter of the rotor magnet, an outer diameter of the second gear is larger than the outer diameter of the first gear, and the second gear is arranged such that the second gear overlaps the rotor magnet with a given distance therebetween. Due to such a constitution, it is unnecessary to interpose other gears between these respective gears and hence, the width dimension of the instrument can be made small.
Further, in the coil instrument of the present invention, a coil supporting portion which supports the respective coils is contiguously formed on the housing. Due to such a constitution, the directions of the winding center axes of the coils and the crossing angle made by both winding center axes can be surely determined and hence, the coils can be held in a stable manner in a state that the directions of the winding center axes of the coils and the crossing angle made by both winding center axes are surely determined.
Further, in the coil instrument of the present invention, the rotor magnet 1 and the first and second gears are accommodated in the housing. Due to such a constitution, the height dimension can be decreased.
Further, in the coil instrument of the present invention, the rotation regulation means which regulates the rotation of the pointer shaft is disposed between the housing and the second gear. Due to such a constitution, the pointer can be surely stopped at a given position (a start position).
Further, in the coil instrument of the present invention, a given region of the outer periphery of the housing excluding a region corresponding to the second gear is covered with a cup-shaped magnetic casing. Due to such a constitution, the magnetic case can be miniaturized and the cost can be reduced.
Further, in the coil instrument of the present invention, a fixed magnet which restricts the movement of the rotor magnet when the respective coils are not energized is provided to the housing. Due to such a constitution, the pointer can be surely held at a given position (a start position) when respective coils are not energized.
Further, in the coil instrument of the present invention, a biasing member which rotates the pointer shaft in one direction when the respective coils are not energized is provided to the pointer shaft. Due to such a constitution, the pointer can be surely returned to a given position (a start position) when respective coils are not energized and further the backlash between the first and second gears can be eliminated.
Further, the coil instrument according to the present invention comprises a rotor shaft having a rotor magnet and a first gear rotatable along with the rotor magnet, a pointer shaft disposed parallel with the rotor shaft and having a second gear connected with the first gear, and a pair of coils arranged at an outer peripheral portion in the radial direction of the rotor magnet where the second gear is not arranged and give a rotational force to the rotor magnet upon energization thereof, wherein the rotor magnet is partially covered with respective coils. Due to such a constitution, the coil instrument can increase the generating torque while maintaining the thin configuration thereof.
Further, the coil instrument according to the present invention comprises a rotor shaft having a rotor magnet and a first gear rotatable along with the rotor magnet, a pointer shaft having a second gear connected with the first gear, a housing supporting the pointer shaft and the rotor shaft in parallel, and a pair of coils arranged at an outer peripheral surface in the radial direction of the rotor magnet where the second gear is not arranged in a state that respective winding central axes of the coils cross each other with a given crossing angle at or in the vicinity of the rotary center of the rotor magnet and give a rotational force to the rotor magnet upon energization thereof, wherein the rotor magnet is partially covered with respective coils. Due to such a constitution, the coil instrument can increase the generating torque while maintaining the thin configuration thereof.
Further, in the coil instrument according to the present invention, the winding diameter of the coils corresponding to at least a radial peripheral surface of the rotor magnet is gradually increased toward the rotor shaft. Due to such a constitution, while ensuring an enough winding quantity, the coil instrument can make the structure compact whereby the space efficiency can be enhanced.
Further, in the coil instrument according to the present invention, the winding frame portions around which the respective coils are wound are contiguously formed on the housing. Due to such a constitution, the directions of the winding center axes of respective coils and the crossing angle made by both winding center axes can be surely determined and hence, the coils can be held in a stable manner in a state that the directions of the winding center axes of the coils and the crossing angle made by both winding center axes are surely determined.